Uplink signaling for dual connectivity

ABSTRACT

The disclosure relates to a method in a wireless device for transmitting an uplink signalling message in a wireless communication network. The wireless device is connected to a first network element over at least a first and a second wireless link. The method comprises determining a transmission mode among alternative transmission modes for transmitting the uplink signalling message. The alternative transmission modes comprise: transmitting on the first wireless link; transmitting on the second wireless link; and transmitting on both the first and the second wireless links. The method also comprises transmitting the uplink signalling message according to the determined transmission mode. The disclosure also relates to a corresponding method performed in the network element, and to the corresponding apparatus.

This application is a continuation of U.S. application Ser. No.16/843,363, filed Apr. 8, 2020, which is a continuation of U.S.application Ser. No. 16/288,474, filed Feb. 28, 2019, now U.S. Pat. No.10,651,964, which is a continuation of U.S. application Ser. No.14/890,452, filed Nov. 11, 2015, now U.S. Pat. No. 10,263,729, which isa 35 U.S.C. § 371 national phase filing of International Application No.PCT/SE2015/050900, filed Aug. 26, 2015, the disclosures of which areincorporated herein by reference in their entireties.

TECHNICAL FIELD

The disclosure generally relates to dual connectivity, and particularlyrelates to methods and apparatus for enabling a wireless device totransmit an uplink signaling message when the wireless device isconnected to a first network element over at least two wireless links.

BACKGROUND

Evolved Packet System (EPS) is the evolved 3rd Generation PartnershipProject (3GPP) Packet Switched Domain. EPS includes Evolved Packet Core(EPC), and Evolved Universal Terrestrial Radio Access Network (E-UTRAN).FIG. 1 shows an overview of the EPC architecture in a non-roamingcontext, which architecture includes a Packet Data Network (PDN) Gateway(PGW), a Serving Gateway (SGW), a Policy and Charging Rules Function(PCRF), a Mobility Management Entity (MME) and a wireless device alsocalled a User Equipment (UE). The radio access network, E-UTRAN,consists of one or more eNodeBs (eNB).

FIG. 2 shows the overall E-UTRAN architecture and includes eNBs,providing the E-UTRA user plane and control plane protocol terminationstowards the UE. The user plane control terminations comprise Packet DataConvergence Protocol (PDCP), Radio Link Control (RLC), Medium AccessControl (MAC), and a Physical Layer (PHY). The control plane controlterminations comprise Radio Resource Control (RRC) in addition to thelisted user plane control terminations. The eNBs are interconnected witheach other by means of an X2 interface. The eNBs are also connected bymeans of the S1 interface to the EPC, more specifically to the MME bymeans of the S1-MME interface and to the SGW by means of the S1-Uinterface. The main parts of the EPC Control Plane and User Planearchitectures are shown in FIG. 3 and FIG. 4, respectively.

Long Term Evolution (LTE) Overview

LTE uses Orthogonal Frequency Division Multiplexing (OFDM) in theDownlink (DL) and Direct Fourier Transform (DFT)-spread OFDM in theUplink (UL). The basic LTE DL physical resource can thus be seen as atime-frequency grid as illustrated in FIG. 5, where each resourceelement corresponds to one OFDM subcarrier during one OFDM symbolinterval.

In the time domain, LTE DL transmissions are organized into radio framesof 10 ms, each radio frame consisting of ten equally-sized subframes oflength T_(frame)=1 ms (see FIG. 6). Furthermore, the resource allocationin LTE is typically described in terms of resource blocks (RB), where aRB corresponds to one slot (0.5 ms) in the time domain and 12 contiguoussubcarriers in the frequency domain. A pair of two adjacent RBs in timedirection (1.0 ms) is known as a RB pair. RBs are numbered in thefrequency domain, starting with 0 from one end of the system bandwidth.The notion of virtual RBs (VRB) and physical RBs (PRB), has beenintroduced in LTE. The actual resource allocation to a UE is made interms of VRB pairs. There are two types of resource allocations,localized and distributed. In the localized resource allocation, a VRBpair is directly mapped to a PRB pair, hence two consecutive andlocalized VRB are also placed as consecutive PRBs in the frequencydomain. On the other hand, the distributed VRBs are not mapped toconsecutive PRBs in the frequency domain; thereby providing frequencydiversity for data channel transmitted using these distributed VRBs.

DL transmissions are dynamically scheduled, i.e., in each subframe thebase station transmits control information about to which terminals datais transmitted and upon which RBs the data is transmitted in the currentDL subframe. This control signaling is typically transmitted in thefirst 1, 2, 3 or 4 OFDM symbols in each subframe and the number n=1, 2,3 or 4 is known as the Control Format Indicator (CFI). The DL subframealso contains Common Reference Symbols (CRS) which are known to thereceiver and used for coherent demodulation of, e.g., the controlinformation. A DL system with CFI=3 is illustrated in FIG. 7.

LTE Control and User Plane Architecture

Conventional control and user plane protocol architectures highlightingthe radio interface on the eNB-side are shown in FIGS. 8a and 8b . Thecontrol and user plane consist of the following protocol layers and mainfunctionality:

-   -   Radio Resource Control, RRC (control plane only)        -   Broadcast of system information for both Non-access stratum            (NAS) and Access stratum (AS)        -   Paging        -   RRC connection handling        -   Allocation of temporary identifiers for the UE        -   Configuration of signaling radio bearer(s) for RRC            connection        -   Handling of radio bearers        -   QoS management functions        -   Security functions including key management        -   Mobility functions including:            -   UE measurement reporting and control of the reporting            -   Handover            -   UE cell selection and reselection and control of cell                selection and reselection        -   NAS direct message transfer to/from the UE    -   Packet Data Convergence Protocol, PDCP        -   There exists one PDCP entity for each radio bearer for the            UE. PDCP is used for both control plane (RRC) and for user            plane        -   Control plane main functions, including            ciphering/deciphering and integrity protection        -   User Plane main functions, including ciphering/deciphering,            header compression and decompression using Robust Header            Compression (ROHC), and in-sequence delivery, duplicate            detection and retransmission (mainly used during handover)    -   Radio Link Control, RLC        -   The RLC layer provides services for the PDCP layer and there            exists one RLC entity for each radio bearer for the UE        -   Main functions for both control and user plane include            segmentation or concatenation, retransmission handling            (using Automatic Repeat Request (ARQ), duplicate detection            and in-sequence delivery to higher layers.    -   Medium Access Control, MAC        -   The MAC provides services to the RLC layer in the form of            logical channels, and performs mapping between these logical            channels and transport channels        -   Main functions are: UL and DL scheduling, scheduling            information reporting, hybrid-ARQ retransmissions and            multiplexing/demultiplexing data across multiple component            carriers for carrier aggregation    -   Physical Layer, PHY        -   The PHY provides services to the MAC layer in the form of            transport channels and handles mapping of transport channels            to physical channels.        -   Main functions for DL performed by the eNB (OFDM) are:            -   Sending of DL reference signals            -   Detailed steps (from “top to down”): Cyclic Redundancy                Check (CRC) insertion; code block segmentation and                per-code-block CRC insertion; channel coding (Turbo                coding); rate matching and physical-layer hybrid-ARQ                processing; bit-level scrambling; data modulation                (Quadrature Phase Shift Keying (QPSK), 16 Quadrature                Amplitude Modulation (QAM), or 64QAM); antenna mapping                and multi-antenna processing; OFDM processing, including                Inverse Fast Fourier Transform (IFFT), and Cyclic Prefix                (CP) insertion resulting in time domain data sometimes                referred to as IQ data or digitalized Radio Frequency                (RF) data); digital-to-analog conversion; power                amplifier; and sending to antenna.        -   Main functions for UL performed by the eNB (DFT-spread OFDM)            are:            -   Random access support        -   Detailed steps (from “top to down”): CRC removal, code block            de-segmentation, channel decoding, rate matching and            physical-layer hybrid-ARQ processing; bit-level            descrambling; data demodulation; Inverse Discrete Fourier            Transform (IDFT); antenna mapping and multi-antenna            processing; OFDM processing, including Fast Fourier            Transform (FFT) and CP removal; Analog-to-Digital            conversion; power amplifier; and receiving from antenna.

The described eNB functionality can be deployed in different ways. Inone example, all the protocol layers and related functionality aredeployed in the same physical node, including the antenna. One exampleof this is a pico or femto eNodeB. Another deployment example is a socalled Main-Remote split. In this case, the eNodeB is divided into aMain Unit and a Remote Unit that are also called Digital Unit (DU) andRemote Radio Unit (RRU) respectively. The Main Unit or DU contains allthe protocol layers, except the lower parts of the PHY layer that areinstead placed in the Remote Unit or RRU. The split in the PHY-layer isat the time domain data level (IQ data, i.e. after/before IFFT/FFT andCP insertion/removal). The IQ data is forwarded from the Main Unit tothe Remote Unit over a so called Common Public Radio Interface (CPRI)which is a high speed, low latency data interface. The Remote Unit thenperforms the needed Digital-to-Analog conversion to create analogRF-data, power amplifies the analog RF-data and forwards the analog RFdata to the antenna. In still another deployment option, the RRU and theantenna are co-located, creating a so called Antenna Integrated Radio(AIR).

Carrier Aggregation

The LTE Rel-10 specifications have been standardized, supportingComponent Carrier (CC) bandwidths up to 20 MHz, which is the maximal LTERel-8 carrier bandwidth. An LTE Rel-10 operation wider than 20 MHz ispossible and appears as a number of LTE CCs to an LTE Rel-10 terminal.The straightforward way to obtain bandwidths wider than 20 MHz is bymeans of Carrier Aggregation (CA). CA implies that an LTE Rel-10terminal can receive multiple CCs, where the CCs have or at least havethe possibility to have, the same structure as a Rel-8 carrier. CA isillustrated in FIG. 9. The Rel-10 standard support up to five aggregatedCCs, where each CC is limited in the RF specifications to have one ofsix bandwidths, namely 6, 15, 25, 50, 75 or 100 RB corresponding to 1.4,3, 5, 10, 15, and 20 MHz respectively. The number of aggregated CCs aswell as the bandwidth of the individual CCs may be different for UL andDL. A symmetric configuration refers to the case where the number of CCsin DL and UL is the same whereas an asymmetric configuration refers tothe case that the number of CCs is different in DL and UL. It isimportant to note that the number of CCs configured in the network maybe different from the number of CCs seen by a terminal. A terminal mayfor example support more DL CCs than UL CCs, even though the networkoffers the same number of UL and DL CCs.

CCs are also referred to as cells or serving cells. More specifically,in an LTE network, the cells aggregated by a terminal are denotedprimary Serving Cell (PCell), and secondary Serving Cell (SCell). Theterm serving cell comprises both PCell and one or more SCells. All UEshave one PCell. Which cell that is a UE's PCell is terminal specific.This PCell is considered “more important”, i.e., vital control signalingand other important signaling is typically handled via the PCell. ULcontrol signaling is always sent on a UE's PCell. The component carrierconfigured as the PCell is the primary CC whereas all other CCs areSCells. The UE can send and receive data both on the PCell and SCells.Control signaling, such as scheduling commands, may be configured to betransmitted and received only on the PCell. However, the commands arealso valid for SCell, and the commands may also be configured to betransmitted and received on both PCell and SCells. Regardless of themode of operation, the UE will only need to read the broadcast channelin order to acquire system information parameters on the PrimaryComponent Carrier (PCC). System information related to the SecondaryComponent Carrier(s) (SCC), may be provided to the UE in dedicated RRCmessages. During initial access, an LTE Rel-10 terminal behaves similarto a LTE Rel-8 terminal. However, upon successful connection to thenetwork, a Rel-10 terminal may—depending on its own capabilities and thenetwork—be configured with additional serving cells in the UL and DL.Configuration is based on RRC. Due to the heavy signaling and ratherslow speed of RRC signaling, it is envisioned that a terminal may beconfigured with multiple serving cells even though not all of them arecurrently used. In summary, LTE CA supports efficient use of multiplecarriers, allowing data to be sent and received over all carriers.Cross-carrier scheduling is supported, avoiding the need for the UE tolisten to all carrier-scheduling channels all the time. A solutionrelies on tight time synchronization between the carriers.

LTE Rel-12 Dual Connectivity

Dual connectivity (DC) is a solution currently being standardized by3GPP to support UEs connecting to multiple carriers to send and receivedata on multiple carriers at the same time. The following is an overviewdescription of DC based on the current 3GPP standard. E-UTRAN supportsDC operation, whereby a UE with multiple receivers and transmitters,which is in RRC_CONNECTED mode, is configured to utilize radio resourcesprovided by two distinct schedulers, located in two eNBs interconnectedvia a non-ideal backhaul over the X2. eNBs involved in DC for a certainUE may assume two different roles. An eNB may either act as a Master eNB(MeNB), or as a Secondary eNB (SeNB). In DC, a UE is connected to oneMeNB and one SeNB. The radio protocol architecture that a particularbearer uses depends on how the bearer is setup. Three alternativesexist: Master Cell Group (MCG) bearer, Secondary Cell Group (SCG)bearer, and split bearer. Those three alternatives are depicted in FIG.10. Signal Radio Bearers (SRBs) are always associated with the MCGbearer and therefore only use the radio resources provided by the MeNB.Note that DC can also be described as having at least one bearerconfigured to use radio resources provided by the SeNB.

Inter-eNB control plane signaling for DC is performed by means of X2interface signaling. Control plane signaling towards the MME isperformed by means of S1 interface signaling. There is only one S1-MMEconnection per UE between the MeNB and the MME. Each eNB should be ableto handle UEs independently, i.e. provide the PCell to some UEs whileproviding SCell(s) for SCG to others. Each eNB involved in DC for acertain UE owns its radio resources and is primarily responsible forallocating radio resources of its cells. Coordination between MeNB andSeNB is performed by means of X2 interface signaling. FIG. 11 showsControl Plane (C-plane) connectivity of eNBs involved in DC for acertain UE. The MeNB is C-plane connected to the MME via S1-MME, theMeNB and the SeNB are interconnected via X2-C. FIG. 12 shows User Plane(U-plane) connectivity of eNBs involved in DC for a certain UE. U-planeconnectivity depends on the bearer option configured. For MCG bearers,the MeNB is U-plane connected to the S-GW via S1-U, and the SeNB is notinvolved in the transport of user plane data. For split bearers, theMeNB is U-plane connected to the S-GW via S1-U and in addition, the MeNBand the SeNB are interconnected via X2-U. For SCG bearers, the SeNB isdirectly connected with the S-GW via S1-U.

Centralization of Radio Access Network (E-UTRAN) Functionality

Possible future evolution of the current Radio Access Network (RAN)architecture has been discussed. From a starting point in a macro sitebased topology, introduction of low power cells, an evolution of thetransport network between different radio base station sites, a radiobase station hardware evolution, and an increased need for processingpower to give some examples, have given rise to new challenges andopportunities. Several strategies are proposed for the RAN architecture,pulling in sometimes different directions. Some strategies, like thegains of coordination, hardware pooling gains, energy saving gains andthe evolution of the backhaul/fronthaul network, are working in favor ofa more centralized deployment. At the same time, other strategies areworking towards de-centralization, such as very low latency requirementsfor some 5G use cases, e.g., mission critical Machine Type Communication(MTC) applications. The terms fronthaul and backhaul are used inrelation to the base station. The traditional definition for fronthaulis the CPRI based fiber link between the baseband Main Unit and theRemote Unit. The backhaul refers to the transport network used forS1/X2-interfaces.

The recent evolution in backhaul/fronthaul technologies has indeedopened up the possibility to centralize the baseband, often referred toas C-RAN. C-RAN is a term that can be interpreted in different ways. Forsome it means a “baseband hotel” like solutions in which the basebandsfrom many sites are collocated to a central site, although there is notight connection and fast exchange of data between the baseband units.The most common interpretation of C-RAN is maybe “Centralized RAN” wherethere is at least some kind of coordination between the basebands. Apotentially attractive solution is the smaller centralized RAN that isbased on a macro base station and the lower power nodes covered by it.In such a configuration, a tight coordination between the macro and thelow power nodes can often give considerable gains. The term “CoordinatedRAN” is an often used interpretation of C-RAN that focuses on thecoordination gains of the centralization. Other more futuristicinterpretations of C-RAN include “cloud” based and “virtualized” RANsolutions where the radio network functionality is supported on generichardware such as general purpose processors, and possibly as virtualmachines.

A centralized deployment can be driven by one or several forces like,e.g., a possible ease of maintenance, upgrade and less need for sites,as well as harvesting of coordination gains. A common misconception isthat there is a large pooling gain and a corresponding hardware savingto be done by the centralization. The pooling gain is large over thefirst number of pooled cells but then diminishes quickly. One keyadvantage of having the basebands from a larger number of sitesco-located and interconnected is the tight coordination that it allows.Examples of these are UL Coordinated Multi-Point (CoMP), and a combiningof several sectors and/or carriers into one cell. The gains of thesefeatures can sometimes be significant in relation to the gains of loosercoordination schemes such as, e.g., enhanced inter-cell interferencecoordination (eICIC) that can be done over standard interfaces (X2)without co-location of the baseband.

An attractive C-RAN deployment from a coordination gain perspective isthe C-RAN built around a larger macro site, normally with severalfrequency bands, and a number of lower power radios, covered by themacro site, that are tightly integrated into the macro over high-speedinterconnect. The largest gains are expected to be seen in deploymentscenarios such as for stadiums and malls. An important consideration forany C-RAN deployment is the transport over the fronthaul, i.e., theconnection between the centralized baseband part and the radios,sometimes referred to as “the first mile”. The cost of the fronthaul,which vary rather greatly between markets, needs to be balanced againstthe benefits.

SUMMARY

For a UE connected to the DC RAN architecture with a radio protocolarchitecture as illustrated in FIG. 10 and further described in thebackground section, there is no known procedure for how to transmituplink signaling messages to the network. If a wireless device isconnected to the network over two or more wireless links, the wirelessdevice needs to know for example on which link to transmit the uplinksignaling message.

An object is to alleviate or at least reduce one or more of the abovementioned problems, and to provide a procedure for transmitting uplinkssignaling messages in a multi-connectivity scenario. This object andothers are achieved by methods, a wireless device, and a network elementaccording to the independent claims, and by the embodiments according tothe dependent claims.

According to a first aspect, a method for transmitting an uplinksignaling message in a wireless communication network is provided. Themethod is performed in a wireless device. The wireless device isconnected to a first network element over at least a first and a secondwireless link. The method comprises determining a transmission modeamong alternative transmission modes for transmitting the uplinksignaling message. The alternative transmission modes comprise:transmitting on the first wireless link; transmitting on the secondwireless link; and transmitting on both the first and the secondwireless links. The method also comprises transmitting the uplinksignaling message according to the determined transmission mode.

According to a second aspect, a method for enabling a wireless device totransmit an uplink signaling message in a wireless communication networkis provided. The method is performed in a first network element. Thewireless device is connected to the first network element over at leasta first and a second wireless link. The method is performed in the firstnetwork element. The method comprises determining at least onetransmission mode among alternative transmission modes for transmittingthe uplink signaling message. The alternative transmission modescomprise: transmitting on the first wireless link; transmitting on thesecond wireless link; and transmitting on both the first and the secondwireless links. The determining is based on criteria for determiningtransmission mode. The method also comprises transmitting information tothe wireless device enabling the wireless device to determinetransmission mode for transmitting the uplink signaling message. Theinformation comprises an indication of the determined at least onetransmission mode.

According to a third aspect, a wireless device configured to transmit anuplink signaling message in a wireless communication network isprovided. The wireless device is connectable to a first network elementover at least a first and a second wireless link. The wireless device isfurther configured to determine a transmission mode among alternativetransmission modes for transmitting the uplink signaling message. Thealternative transmission modes comprise: transmitting on the firstwireless link; transmitting on the second wireless link; andtransmitting on both the first and the second wireless links. Thewireless device is also configured to transmit the uplink signalingmessage according to the determined transmission mode.

According to a fourth aspect, a first network element configured toenable a wireless device to transmit an uplink signaling message in awireless communication network is provided. The wireless device isconnectable to the first network element over at least a first and asecond wireless link. The first network element is further configured todetermine at least one transmission mode among alternative transmissionmodes for transmitting the uplink signaling message. The alternativetransmission modes comprise: transmitting on the first wireless link;transmitting on the second wireless link; and transmitting on both thefirst and the second wireless links. The determining is based oncriteria for determining transmission mode. The first network element isalso configured to transmit information to the wireless device enablingthe wireless device to determine transmission mode for transmitting theuplink signaling message, the information comprising an indication ofthe determined at least one transmission mode.

According to further aspects, computer programs and computer programproducts corresponding to the aspects above are provided.

One advantage of embodiments is that a procedure for how a wirelessdevice transmits uplink signaling messages in a multi-connectivityscenario is provided. Another advantage is that a transmission mode fortransmitting the uplink signaling message may be adapted to a currentsituation such as e.g. a capability of the wireless device or a loadsituation.

Other objects, advantages and features of embodiments will be explainedin the following detailed description when considered in conjunctionwith the accompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of embodiments disclosed herein, includingparticular features and advantages thereof, will be readily understoodfrom the following detailed description and the accompanying drawings.

FIG. 1 is a block diagram schematically illustrating a non-roaming EPCarchitecture for 3GPP accesses.

FIG. 2 is a block diagram schematically illustrating an E-UTRAN overallarchitecture.

FIG. 3 schematically illustrates an EPC Control Plane protocolarchitecture.

FIG. 4 schematically illustrates an EPC User Plane protocolarchitecture.

FIG. 5 schematically illustrates the basic LTE DL physical resource.

FIG. 6 schematically illustrates an LTE time-domain structure.

FIG. 7 schematically illustrates a DL subframe.

FIGS. 8a and 8b schematically illustrate control and user plane protocollayers for a conventional eNB radio interface.

FIG. 9 schematically illustrates CA of five CC.

FIG. 10 schematically illustrates a Radio Protocol Architecture for DC.

FIG. 11 is a block diagram schematically illustrating C-Planeconnectivity of eNBs involved in DC.

FIG. 12 is a block diagram schematically illustrating U-Planeconnectivity of eNBs involved in DC.

FIG. 13 schematically illustrates one example of a functional splitbetween network elements.

FIGS. 14a and 14b schematically illustrate an eNB split into eNB-a andeNB-s.

FIG. 15 schematically illustrates DC with functional split establishedfor a wireless device.

FIG. 16 schematically illustrates a Multi-RAT DC established for awireless device.

FIG. 17 is a signaling diagram schematically illustrating signalingbetween UE and network according to embodiments.

FIGS. 18a through 18e are flow charts schematically illustratingembodiments of a method for a wireless device according to variousembodiments.

FIG. 19 is a flow chart schematically illustrating embodiments of amethod for a network element according to various embodiments.

FIGS. 20a through 20c are block diagrams schematically illustratingembodiments of the wireless device and the network element according tovarious embodiments.

DETAILED DESCRIPTION

In the following, different aspects will be described in more detailwith references to certain embodiments and to accompanying drawings. Forpurposes of explanation and not limitation, specific details are setforth, such as particular scenarios and techniques, in order to providea thorough understanding of the different embodiments. However, otherembodiments that depart from these specific details may also exist.

Ongoing discussions in the wireless industry in different for a seem tomove towards a direction where the functional architecture of the 5Gradio access network should be designed flexibly enough to be deployedon different hardware platforms and possibly on different sites of thenetwork. A functional split as illustrated in FIG. 13 has been proposed.In this example, the RAN functions are classified in synchronousfunctions (SF) and asynchronous functions (AF). Asynchronous functionsare functions with loose timing constraints, and synchronous functionsare typically executing time critical functionality. The synchronousnetwork functions have requirements on processing timing which arestrictly dependent on timing of a radio link used for communicating withthe wireless device. Strictly dependent means that the timing of theradio link is crucial for the synchronous network functions to work asintended. The asynchronous network functions have requirements onprocessing timing not strictly dependent on the timing of the radiolink, or even independent of the timing of the radio link. Thesynchronous functions may be placed in a logical node called eNB-s andthe asynchronous functions may be placed in a logical node called eNB-a.The instances of functions associated to the eNB-s, i.e. the synchronousfunctions, may be placed at a network element close to the airinterface. The synchronous functions will form what is called asynchronous function group (SFG). The instances of the asynchronousfunctions associated to the eNB-a can be flexibly instantiated either atthe network element close to the air interface, i.e. at the same networkelement as the eNB-s functions or in other network elements such asfixed network nodes (FNNs). If it is assumed that the functions areE-UTRAN functions, the split of functions may lead to the functionalarchitecture for the control plane and the user plane illustrated inFIGS. 14a and 14b , where one new interface will be needed.

In order to support DC or multi-connectivity features, such as userplane aggregation for aggregated data rates, or control/user planediversity for e.g. reliability and fast packet switching, instances ofasynchronous functions can be made common to multiple instances ofsynchronous functions. In other words, a same instance of a functionassociated to an eNB-a can control multiple instances of a functionassociated to an eNB-s. In the case of the current LTE functionality(see section “LTE control and user plane architecture” above), this maylead to common instances for RRC and PDCP functions associated to Nmultiple instances of RLC/MAC/PHY. N is the number of links that the UEcan be connected over at the same time. One example scenario isillustrated In FIG. 15 where the UE is connected over two links via bothnetwork element eNB-s1 and network element eNB-s2 to network elementeNB-a. The network element eNB-a comprises in general the asynchronousfunctions, i.e. the protocols that are common for both control plane(RRC and PDCP) and user plane (PDCP).

It is envisioned that 5G radio accesses will be composed by multiple airinterfaces, e.g. air interface variants or air interfaces for differentRATs. These multiple air interfaces may be tightly integrated, meaningthat it is possible to have common function instances for multiple airinterfaces. It is also envisioned that one of the air interfaces in a 5Gscenario may be LTE-compatible, e.g. an evolution of LTE, while anotherone is non-LTE compatible. Therefore, in order to address such amulti-RAT integrated architecture, the multi-connection scenario mustsupport network elements or logical nodes from different accesstechnologies. The non-LTE-compatible network elements are likely tosupport different lower layer protocols than LTE-compatible networkelements support, e.g. due to the high frequencies a 5G network issupposed to operate on and the new use cases it is required to address.Therefore standardized CA between LTE and the new 5G radio accesses maynot be possible. The standardized DC solution contains different levelsof user plane aggregation but no means for Dual Control Plane betweentwo different LTE-carriers or between LTE-compatible andnon-LTE-compatible carriers.

Therefore, the previously described functional split between eNB-a andeNB-s can be extended so that the same instance of asynchronousfunctions are defined for multiple air interfaces, where the UE can beconnected over the multiple air interfaces at the same time or duringmobility procedures. The multiple air interfaces will then havedifferent synchronous functional groups per air interface, e.g. forcompatible-LTE and non-compatible LTE parts of the 5G radio access.

The split illustrated in FIG. 13 may be applied to DC between differentRATs, e.g. one LTE RAT and one 5G RAT. In this case the eNB-a cancomprise common support for both control and user plane for theasynchronous functions. An eNB-s for each RAT contains the synchronousfunctions, thus enabling that the synchronous functions areRAT-specific, e.g. different for LTE RAT and 5G RAT. Such a scenario isshown in FIG. 16 where the eNB-a is called “5G & LTE eNB-a” and theeNB-s are called “LTE eNB-s1” and “5G eNB-s2” respectively.

The functional split and RAN architecture such as the one describedabove with reference to FIGS. 15 and 16, or any other RAN functionalsplit where groups of functions are instantiated in different networkelements, implies a possibility to have common function instance(s)associated to multiple network elements and/or links from the same ormultiple air interfaces.

Embodiments are described in a non-limiting general context in relationto transmission of a measurement report—being the uplink signalingmessage—by a UE in the example scenario illustrated in FIG. 15. The UEis connected to the eNB-a over a first and a second wireless link. Thenetwork functions serving the UE over the first wireless link are inthis example scenario split between eNB-a and eNB-s1, which may bereferred to as the first and the second network elements respectively.The network functions serving the UE over the second wireless link aresplit between eNB-a and eNB-s2, where eNB-s2 may be referred to as thethird network element. Some or all of these network elements may be partof a same physical network node, or they may each be separate physicalnetwork elements. The network functions are in the example scenariosplit between eNB-a and eNB-s1/e-NB-s2 based on whether they areasynchronous or synchronous. The same instance of asynchronous functionseNB-a may be defined for multiple air interfaces, where the UE can beconnected over the multiple air interfaces corresponding to the twowireless links at the same time. The multiple air interfaces will thenbe associated with different synchronous function groups per airinterface. eNB-s1 and eNB-s2 in FIG. 15 may be from the same RAT, andmay be owned by the same operator or by different operators.Alternatively, eNB-s1 and eNB-s2 may be from respective different RATs,e.g. LTE-compatible and non-LTE-compatible 5G accesses, as illustratedin FIG. 16. Also in this second case they may be owned by the sameoperator or by different operators. The embodiments described herein aremainly given in the context of multiple RATs, for example LTE and 5GRATs. However, the described embodiments may also apply for single RATcases, especially in the cases when a single eNB-s is connected tomultiple different operator networks, as in these cases a single RAT maybe used for both the first and second wireless links.

Although the functions in this example scenario are differentiated basedon whether they are synchronous or not, it should be noted thatembodiments of the invention may be applied to any other networkfunction architecture where the network functions are split into twonetwork elements based on some other criteria than whether the functionis synchronous or not. One example is to split functions in a multi-RATscenario based on whether they are common for the multiple RATs orspecific to one of the RATs.

Furthermore, the described embodiments may also apply for a pure DCscenario without the split of the network functions on two networkelements. In that case, the wireless device is connected directly to thefirst network element via the two links, without involving the secondand the third network element.

Furthermore, although embodiments are described in relation to a DCscenario, the embodiments may also be applied to a scenario where the UEenters multi-connectivity, where “multi” implies more than dual, i.e.more than two, by adding yet another link that can be from the same orfrom a different access layer or RAT than the other links. The procedurefor transmitting uplink signaling messages in a multi-connectivityscenario is similar to the transmission of uplink signaling messages inthe above described DC scenario, and embodiments of the invention maythus easily be applicable to the multi-connectivity scenario.

Transmission Modes

The problem of non-existing procedures for transmitting measurementreports to the network in a DC scenario, e.g. with split functionalitysuch as in the example scenario illustrated in FIG. 16, is addressed bya solution where the UE determines on which wireless link or links totransmit the measurement report. The UE determines a transmission modeamong alternative transmission modes for transmitting the measurementreport. The alternative transmission modes comprise:

-   -   transmitting on the first wireless link;    -   transmitting on the second wireless link;    -   transmitting on both wireless links.        The determined transmission mode is then used when transmitting        the measurement report.

The transmission mode to transmit on both wireless links is particularlyuseful for measurement reports that are to be sent once and/ormeasurement reports which should not be lost, such as event-triggeredmeasurement reports. In addition, if unacknowledged uplink signalingprocedures are introduced, the transmission mode to transmit on bothwireless links may be suitable for an unacknowledged measurement report.The transmission mode to transmit on one of the wireless links is on theother hand particularly useful for periodic measurement reports. Thistransmission mode has the advantage of reducing the amount ofmeasurement report transmissions. As will be further described below,what wireless link to choose may be determined in different ways, suchas by using a predetermined rule or scheme, e.g. taking into accountaspects like channel conditions, nature of the signaling procedure,expected latency, required transmission power and user specific or UEspecific policies. In one example, the choice of wireless link for thetransmission is based on the type of uplink signaling message ormeasurement report. In another example, each time a measurement reportis to be transmitted the UE autonomously chooses one link randomly orbased on e.g. a round-robin rule.

In embodiments, the UE may also determine how to perform retransmissionsas part of determining the transmission mode. In one exemplaryembodiment, the UE determines to transmit the measurement report on bothlinks. Furthermore, the UE determines to repeatedly retransmit themeasurement report on both links and stops retransmitting when gettingan acknowledgement (ACK) or a response confirming that the measurementreport has been received by the network on one of the links. In anotherexemplary embodiment, the UE transmits the measurement report on one ofthe wireless links, and in absence of ACK or response it retransmits themeasurement report on the other wireless link. These embodimentsincrease the robustness for measurement reporting, by introducingdiversity for the measurement reports transmitted by the UE.

FIG. 17 is a signaling diagram illustrating one example of signalingbetween the UE 1750 and the network in the embodiment where the UErepeatedly transmits the measurement report on both links, and stopstransmitting when getting an ACK on one of the links. In S1a and S1b,the UE 1750 transmits a measurement report on each of the links. Thesemessages are both lost (illustrated by dashed signal arrows), i.e. thenetwork never receives the measurement report. In S2a and S2b, the UE1750 retransmits the measurement reports on both links. Theretransmission S2a of the measurement report is received by LTE eNB-s11720 over the first link, and is forwarded and received by 5G & LTEeNB-a1 1700 in S2c. 5G & LTE eNB-a1 1700 in turn transmits a Measurementreport ACK to the UE 1750 over the two links, in S3a and S3b. In theexample, only the Measurement report ACK transmitted over the secondlink by 5G eNB-s2 1730 is received by the UE 1750 in S3d. TheMeasurement report ACK transmitted over the first link in S3c is lost.The UE 1750 may already have started a second retransmission of themeasurement report (not illustrated) before it receives the Measurementreport ACK in S3d. However, when it receives the Measurement report ACKmessage S3d via the 5G eNB-s2 1730 it stops retransmitting in 171. Theabove described transmission mode with retransmissions require that themeasurement report has a suitable downlink acknowledgement message, suchas the Measurement report ACK in this example, which is sent by thenetwork in response to the received Measurement report. Thistransmission mode with retransmissions is particularly useful insituations where the channel conditions are poor for both wirelesslinks.

Determining the Transmission Mode

In one embodiment of the invention, the determining of the transmissionmode is performed autonomously by the UE. In an alternative embodiment,the determining is performed by the network and the network subsequentlyinforms the UE of the determined transmission mode, e.g. through aconfiguration of the UE using a configuration message such as an RRCConnection Reconfiguration message. However, in another embodiment,determining of the transmission mode is a combination of the twoprevious embodiments, where the network determines a set of possibletransmission modes and configures or informs the UE accordingly, wherebythe UE makes the final decision on what transmission mode to use.

The wireless device may determine the transmission mode after themeasurement report is generated. However, it may also be performed inthe opposite order, i.e. the measurement report is generated after thetransmission mode is determined. The transmission mode may e.g. besignaled by the network to the UE in an uplink grant message or ascheduling command. In such a case it may be possible to signal thetransmission mode before the generation of every measurement report. Inanother embodiment, the UE may receive configuration rules as part of anRRC message enabling the UE to determine the transmission mode, and thetransmission mode will thus be determined by the UE before thegeneration of a measurement report. In still another exemplaryembodiment, the measurement report is generated by e.g. the RRC layerand is queued by lower layers, and the lower layers may then determinethe transmission mode just before the measurement report is delivered.

In the embodiments described above, the determining of transmission modemay be based on one or more criteria for determining the transmissionmode. The criteria are listed below. For the embodiment when the UEdetermines the transmission mode autonomously, it is thus the UE thatmakes use of the criteria for determining the transmission mode. When itis the network that determines the transmission mode, the networkcorrespondingly uses the criteria for the determination. In someembodiments, both the network and the UE make use of the criteria, whichmay be the same or different criteria. The criteria used respectively bythe network and the UE may differ, because the network and the UE maynot have access to the same information. In the below list of criteria,each criterion is applicable for both the UE and the network when notstated otherwise.

List of Criteria for Determining Transmission Mode Channel Quality

The channel quality of the wireless links over which the UE is connectedto the network may be used as criterion for determining the transmissionmode. The UE and/or the network may measure the channel quality ofeither a subset of or all of the wireless links. If the network ismeasuring the channel quality, the UE may receive reports or indicationsof the channel quality from the network. The UE or the network may usethe channel quality to determine the transmission mode, and therebyincreasing the probability for a transmitted measurement report to reachthe network. In one exemplary embodiment, the UE may determine totransmit the measurement report on the first wireless link if thechannel quality of the first wireless link is better than the channelquality of the second wireless link, and if the channel quality of thefirst wireless link is above a quality threshold. In another embodiment,the UE may determine to transmit the measurement report on both thefirst and the second wireless link if the channel quality of the firstwireless link is similar to the channel quality of the second wirelesslink, and if the channel quality of the first and the second wirelesslinks is equal to or lower than the quality threshold. The channelquality may be determined to be similar e.g. when the channel qualitydifference is less than a given value. In this latter embodiment, the UEmay optionally determine that the measurement report shall beretransmitted on both links until an acknowledgement message has beenreceived from the network on either of the links. This may e.g. bedetermined when the measurement report to transmit is categorized as“important”, which may be done depending on the type of measurementreport and the situation (see e.g. below in the list of criteria under“Type of uplink signaling message”). An example of such an “important”measurement report is an event triggered measurement report, whichsupposedly will trigger a handover because of the poor channel qualityof both wireless links and therefore is important with regards toperformance.

Load

The load on the wireless links over which the UE is connected to thenetwork may be used as criterion for determining the transmission mode.The UE and/or the network may use the load of both or either of thelinks when selecting the transmission mode. This makes it possible toreduce the load impact on the system for transmitting measurementreports. The load of a given link can be obtained by e.g. measuring thereceived signal power on the uplink frequency band. Alternatively, theload can be obtained by checking the throughput or the size of thescheduling queues.

UE Capability

The UE capability may be used as criterion for determining thetransmission mode. The UE may e.g. be capable of using the firstwireless link but not the second wireless link, and may thus determineto transmit the measurement report only on the first wireless link. Asone example this may be the case when the two links correspond to twodifferent RATs respectively such as one LTE compatible and one non-LTEcompatible RAT, and the UE is LTE capable only.

Resiliency/Redundancy/Robustness

Resiliency, redundancy, or robustness requirements may be used ascriterion for determining the transmission mode. The UE may e.g.determine to transmit the measurement report on one of the links, andmay then—for robustness reasons—determine to retransmit the measurementreport on the other link if no acknowledgement is received.

Service Requirement/QoS

The requirements of an active service or the QoS of the bearer, whichmay be the only way the RAN is aware of the service requirements, maygovern the determining of transmission mode. For instance, transmittingthe same packets on both wireless links simultaneously may be chosen ifrobustness and/or low latency is required by the service andretransmissions therefore should be avoided. Another example is totransmit different packets on different wireless links to increase thethroughput. This may apply specifically for the case when different QoScan be signaled for the signaling bearers of different UEs.

Latency

The latency of the wireless links over which the UE is connected to thenetwork may be used as criterion for determining the transmission mode.In one example, the measurement report is transmitted on the wirelesslink with the lowest latency. In order to obtain the latency of a link,the UE may in one example transmit an Internet Protocol version 4 (IPv4)ping on the two links and compare the ping responses. Another example ofhow to obtain a latency value for the links is to use pre-configured(e.g. hardcoded) values of an assumed latency ranking order fordifferent links in case the two links use different RATs respectively.

Type of Uplink Signaling Message

The type of the uplink signaling message that is to betransmitted/received can be used as input for determining thetransmission mode. In one example, the transmission mode for ameasurement report is determined to be to transmit on one of thewireless links, while the transmission mode for all other uplinksignaling messages is determined to be to transmit on both wirelesslinks. In general, the choice of transmission mode may depend on theimportance or urgency of the uplink signaling message, or it may dependon whether an acknowledgement is expected for the uplink signalingmessage or not.

In case the uplink signaling message is a measurement report, thetransmission mode may be determined based on the type of measurementreport. In one example, the transmission mode for a periodic measurementreport is determined to be to transmit on one of the links, while thetransmission mode for an event-triggered measurement report isdetermined to be to transmit on both of the links.

Transmission Mode of Corresponding Downlink Signaling Message

In case the uplink signaling message is a response to a downlinkmessage, the transmission mode may be determined based on thetransmission mode used for the downlink. For instance, the uplinkmessage may be transmitted on the same wireless link or links as thedownlink message was received on. Alternatively, the UE may beconfigured to transmit the uplink signaling message on a certain otherlink than the link the downlink message was received on (uplink-downlinkseparation). The network may determine the transmission mode when adownlink signaling message is to be transmitted, and configure the UEwith the transmission mode implicitly by transmitting the downlinksignaling message on a given wireless link.

Acknowledgment of Uplink Signaling Message

Another alternative embodiment is to determine the transmission modebased on whether the uplink signaling message is acknowledged orresponded to by the receiver in the network according to the specifiedsignaling protocol. For instance, the UE may transmit an uplinksignaling message to be acknowledged on one wireless link, while anuplink signaling message for which no acknowledgement is expected istransmitted on both wireless links.

Carrier Aggregation (CA)

The uplink usage of each of the wireless links may be a criterion to usefor determining transmission mode. The uplink usage may e.g. be thatthey use LTE and 5G CA or dual connectivity. For example, if CA isapplied on the LTE-side, in addition to dual connectivity between LTEand 5G, then a message can be sent only via LTE. CA positively affectsthe performance of the LTE link, and therefore the LTE link ispreferred.

Backhaul Quality

The backhaul quality from 5G eNB-s2 to eNB-a1 and the backhaul qualityfrom LTE eNB-s1 to eNB-a1 may be used as criteria for determining thetransmission mode. The principle is that the backhaul with the betterquality is prioritized over the backhaul with the lower quality. TheeNB-a1 can measure the links to the different eNB-s1 and eNB-s2, and theUE may be informed about the backhaul quality of a particular link, e.g.via broadcast or dedicated signaling.

Mobility/Speed of UE

The mobility or speed of the UE may be used as criteria for determiningthe transmission mode. If the UE is moving fast, for example when theUE's speed is measured to be above a specified limit, or when the UE isidentified to be in a specific mobility state, a wireless linkcorresponding to the widest coverage area of the different links ispreferred. For example, an LTE link may be preferred in the case whenLTE is deployed on a lower frequency band than the frequency band of the5G link.

QoS

Agreed or expected QoS on the different links may be used as criteriafor determining the transmission mode. The different links may beassociated with different QoS through explicit signaling. Alternatively,the QoS may be measured for the different links.

Predetermined Rule

A predetermined rule, such as a round-robin rule, may be used todetermine the transmission mode. One example of a predetermined rule isto determine that the UE transmits every second measurement report onthe first wireless link, and every other second measurement report onthe second wireless link.

Random Selection

The criterion for determining the transmission mode may be to randomlyselect one wireless link between the available wireless links for thetransmission of the measurement report.

Embodiments of Methods Described with Reference to FIGS. 18a Through 18eand 19

FIG. 18a is a flowchart illustrating one embodiment of a method fortransmitting an uplink signaling message in a wireless communicationnetwork. A wireless device is connected to a first network element overat least a first and a second wireless link. The wireless device may beany kind of device such as a UE, a mobile terminal, a sensor, or alaptop. The method is performed in the wireless device and comprises:

-   -   1810: Determining a transmission mode among alternative        transmission modes for transmitting the uplink signaling        message. The alternative transmission modes comprise:        transmitting on the first wireless link; transmitting on the        second wireless link; and transmitting on both the first and the        second wireless links. The advantages of the different        transmission modes are further described in the section        “Transmission modes” above. In embodiments, the determining of        the transmission mode is based on criteria for determining        transmission mode.    -   1820: Transmitting the uplink signaling message according to the        determined transmission mode.

In the section “Determining the transmission modes” above, differentembodiments related to how the determining may be done are described.The determining may e.g. be performed autonomously by the wirelessdevice, may be performed solely by the network which then configures thewireless device to transmit accordingly, or it may be a combineddetermining by both the network and the wireless device. The network mayhave better knowledge than the wireless device of certain criteria fordetermining the transmission mode or vice versa. The embodimentsdescribed below with reference to FIGS. 18b and 18c explain some ofthese alternative embodiments.

FIG. 18b is a flowchart illustrating an embodiment of the method in thewireless device, where the network transmits information to the wirelessdevice that enables the device to determine the transmission mode basedon some criteria. The network may e.g. send an indication of twotransmission modes to the wireless device, and the wireless device maythen determine or select one of the indicated transmission modes basedon some criteria for determining the transmission mode. The method mayin this embodiment comprise:

-   -   1800: Receiving information from the first network element,        indicating at least one of the alternative transmission modes.        Although the first network element is involved in the        transmission of the information to the wireless device, the        origin of the information may be another network node of the        wireless communication network.    -   1810: Determining the transmission mode based on the received        information. In embodiments, the determining of the transmission        mode is based on criteria for determining transmission mode. The        criteria may e.g. be channel quality measured by the wireless        device.    -   1820: Transmitting the uplink signaling message according to the        determined transmission mode.

FIG. 18c is a flowchart illustrating another embodiment of the method inthe wireless device, where the network transmits both the transmissionmode indications and the criteria for determining the transmission mode.This enables the wireless device to determine the transmission modebased on the information from the network. The network may e.g. transmittwo alternative transmission modes as well as load values for the twolinks, and the wireless device can then determine the best transmissionmode, given the type of uplink signaling message to transmit, based onthe received information from the network. The method may thus comprise:

-   -   1800: Receiving information from the first network element,        indicating at least one of the alternative transmission modes.    -   1805: Receiving criteria for determining transmission mode from        the first network element.    -   1810: Determining the transmission mode based on the received        information and the received criteria for determining        transmission mode. The determining may also be based on criteria        for determining transmission mode known by the wireless device,        such as the type of uplink signaling message to transmit.    -   1820: Transmitting the uplink signaling message according to the        determined transmission mode.

As described in the section “Transmission modes” above, determining thetransmission mode may also comprise determining on which link toretransmit the uplink signaling message. FIG. 18d is a flowchartillustrating one such embodiment of the method in the wireless devicewhich may be combined with any of the above described embodiments. Inthis embodiment, the determining 1810 of the transmission mode maycomprise:

-   -   1811: Determining to transmit the uplink signaling message on        both the first and the second wireless links.    -   1812: Determining to repeatedly retransmit the uplink signaling        message on both wireless links until an acknowledgement of the        uplink signaling message is received on at least one of the        first and the second wireless links.

Furthermore, the method may comprise the transmitting 1820 of the uplinksignaling message according to the determined transmission mode, i.e.first transmitting on both links and then retransmitting on both linksif no acknowledgement is received for the first transmission. FIG. 18eis a flowchart illustrating another such embodiment of the method in thewireless device which may be combined with any of the embodimentsdescribed with reference to FIGS. 18a through 18c . In this embodiment,the determining 1810 of the transmission mode may comprise:

-   -   1815: Determining to transmit the uplink signaling message on        the first wireless link.    -   1816: Determining to retransmit the uplink signaling message on        the second wireless link if no acknowledgement is received for        the uplink signaling message transmitted on the first wireless        link.

Furthermore, the method may comprise the transmitting 1820 of the uplinksignaling message according to the determined transmission mode, i.e.first transmitting on one link and retransmitting on the other link ifno acknowledgement is received for the first transmission.

In any of the embodiments of the method in the wireless device describedwith reference to FIGS. 18a through 18e , the criteria for determiningtransmission mode may be related to at least one of the following:

-   -   a channel quality of at least one of the first and the second        wireless links;    -   a load on at least one of the first and the second wireless        links;    -   a wireless device capability of using at least one of the first        and the second wireless links;    -   a quality of service of a bearer associated with the uplink        signaling message;    -   a latency of at least one of the first and the second wireless        links;    -   a type of uplink signaling message;    -   a transmission mode of a downlink signaling message to which the        uplink signaling message is a response;    -   whether the uplink signaling message is acknowledged or not;    -   use of carrier aggregation on at least one of the first and the        second wireless links;    -   a speed of the wireless device;    -   a quality of service associated with at least one of the first        and the second wireless links;    -   a pre-determined rule for determining the transmission mode;    -   a random selection of at least one of the first and the second        wireless links.

Furthermore, in any of the embodiments described above, the determining1810 of the transmission mode may comprise obtaining the channel qualityof at least one of the first and the second wireless links anddetermining the transmission mode based on the obtained channel quality.The obtaining of the channel quality may comprise at least one ofmeasuring the channel quality and receiving the channel quality from thefirst network element.

In one embodiment, the channel quality of both the first and the secondwireless links are obtained. The determining 1810 of the transmissionmode based on the obtained channel quality may then comprise determiningto transmit the uplink signaling message on the wireless link withhighest obtained channel quality, when the highest obtained channelquality is equal to or above a threshold value. On the other hand, whenthe highest obtained channel quality is below the threshold value, thedetermining 1810 of the transmission mode may comprise determining totransmit the uplink signaling message on both the first and the secondwireless links.

FIG. 19 is a flowchart illustrating one embodiment of a method forenabling a wireless device to transmit an uplink signaling message in awireless communication network. The wireless device is connected to afirst network element over at least a first and a second wireless link.The method is performed in the first network element and comprises:

-   -   1910: Determining at least one transmission mode among        alternative transmission modes for transmitting the uplink        signaling message. The alternative transmission modes comprise:        transmitting on the first wireless link; transmitting on the        second wireless link; and transmitting on both the first and the        second wireless links. The determining of at least one        transmission mode is based on criteria for determining        transmission mode.    -   1920: Transmitting information to the wireless device enabling        the wireless device to determine transmission mode for        transmitting the uplink signaling message, the information        comprising an indication of the determined at least one        transmission mode. The transmitted information may further        comprise the criteria for determining transmission mode.        The method may in embodiments also comprise receiving the uplink        signaling message from the wireless device in accordance with        one of the alternative transmission modes.

The criteria for determining transmission mode may be related to atleast one of the following:

-   -   a channel quality of at least one of the first and the second        wireless links;    -   a load on at least one of the first and the second wireless        links;    -   a wireless device capability of using at least one of the first        and the second wireless links;    -   a quality of service of a bearer associated with the uplink        signaling message;    -   a latency of at least one of the first and the second wireless        links;    -   a type of uplink signaling message;    -   a transmission mode of a downlink signaling message to which the        uplink signaling message is a response;    -   whether the uplink signaling message is acknowledged or not;    -   use of carrier aggregation on at least one of the first and the        second wireless links;    -   a speed of the wireless device;    -   a quality of service associated with at least one of the first        and the second wireless links;    -   a pre-determined rule for determining the transmission mode;    -   a random selection of at least one of the first and the second        wireless links.

As already mentioned, the uplink signaling message may in any of theembodiments described above be a measurement report. Furthermore, thefirst and the second wireless links may be both associated with one RAT,or each associated with respective different RATs as described withreference to FIGS. 15 and 16.

The functionality split described e.g. with reference to FIG. 13 abovemay also be applied in embodiments. In such an embodiment, networkfunctions serving the wireless device over the first wireless link aresplit between the first network element and a second network element.Network functions serving the wireless device over the second wirelesslink are split between the first network element and a third networkelement. In the example scenario in FIGS. 15 and 16 the first networkelement corresponds to the eNB-a, the second network element correspondsto eNB-s1, and the third network element corresponds to eNB-s2. Asdescribed above, the network functions of the first network element maybe asynchronous network functions, and the network functions of thesecond and third network elements may be synchronous network functions.The synchronous network functions of the second network element may haverequirements on processing timing which are strictly dependent on timingof the first wireless link. The synchronous network functions of thethird network element may have requirements on processing timing whichare strictly dependent on timing of the second wireless link.Furthermore, the asynchronous network functions may have requirements onprocessing timing not strictly dependent on the timing of any of thefirst or second wireless links.

Embodiments of Apparatus Described with Reference to FIGS. 20a Through20c Wireless Device

An embodiment of a wireless device 2050 is schematically illustrated inthe block diagram in FIG. 20a . The wireless device is configured totransmit an uplink signaling message in a wireless communicationnetwork. The wireless device 2050 is connectable to a first networkelement 2000 over at least a first and a second wireless link. Thewireless device 2050 is further configured to determine a transmissionmode among alternative transmission modes for transmitting the uplinksignaling message. The alternative transmission modes comprise:transmitting on the first wireless link; transmitting on the secondwireless link; and transmitting on both the first and the secondwireless links. The wireless device 2050 is also configured to transmitthe uplink signaling message according to the determined transmissionmode.

In embodiments, the wireless device 2050 may be further configured toreceive information from the first network element 2000, indicating atleast one of the alternative transmission modes, and to determine thetransmission mode based on the received information. The wireless device2050 may be configured to determine the transmission mode based oncriteria for determining transmission mode. As another option, thewireless device 2050 may be configured to receive the criteria fordetermining transmission mode from the first network element 2000.

In other embodiments, the wireless device 2050 may be configured todetermine the transmission mode by being configured to obtain thechannel quality of at least one of the first and the second wirelesslinks, and determine the transmission mode based on the obtained channelquality. The obtaining may comprise at least one of measuring thechannel quality and receiving the channel quality from the first networkelement 2000. In embodiments, the wireless device 2050 may be furtherconfigured to obtain the channel quality of both the first and thesecond wireless links, and to determine the transmission mode based onthe obtained channel quality by being configured to determine totransmit the uplink signaling message on the wireless link with highestobtained channel quality, when the highest obtained channel quality isequal to or above a threshold value. When the highest obtained channelquality is below the threshold value, the wireless device 2050 may befurther configured to determine the transmission mode based on theobtained channel quality by being configured to determine to transmitthe uplink signaling message on both the first and the second wirelesslinks.

In embodiments, the wireless device 2050 may be further configured todetermine the transmission mode by being configured to determine totransmit the uplink signaling message on both the first and the secondwireless links, and determine to repeatedly retransmit the uplinksignaling message on both wireless links until an acknowledgement of theuplink signaling message is received on at least one of the first andthe second wireless links.

As an alternative, the wireless device 2050 may be further configured todetermine the transmission mode by being configured to determine totransmit the uplink signaling message on the first wireless link, anddetermine to retransmit the uplink signaling message on the secondwireless link if no acknowledgement is received for the uplink signalingmessage transmitted on the first wireless link.

In any of the embodiments above, the uplink signaling message may be ameasurement report. Furthermore, the first and the second wireless linksmay be both associated with one RAT, or each associated with respectivedifferent RATs.

The functionality split described e.g. with reference to FIG. 13 abovemay also be applied in embodiments. In such an embodiment, networkfunctions serving the wireless device over the first wireless link aresplit between the first network element and a second network element.Network functions serving the wireless device over the second wirelesslink are split between the first network element and a third networkelement. In the example scenario in FIGS. 15 and 16 the first networkelement corresponds to the eNB-a, the second network element correspondsto eNB-s1, and the third network element corresponds to eNB-s2. Asdescribed above, the network functions of the first network element maybe asynchronous network functions, and the network functions of thesecond and third network elements may be synchronous network functions.The synchronous network functions of the second network element may haverequirements on processing timing which are strictly dependent on timingof the first wireless link. The synchronous network functions of thethird network element may have requirements on processing timing whichare strictly dependent on timing of the second wireless link.Furthermore, the asynchronous network functions may have requirements onprocessing timing not strictly dependent on the timing of any of thefirst or second wireless links.

As illustrated in FIG. 20a , the wireless device 2050 may comprise aprocessing circuit 2051 and a memory 2052 in embodiments of theinvention. The wireless device 2050 may also comprise a communicationinterface circuit 2053 configured to communicate with the first networkelement over the first and second wireless links. The communicationinterface circuit 2053 may in embodiments comprise a transceiver adaptedto communicate wirelessly with the network. The memory 2052 may containinstructions executable by said processing circuit 2051, whereby thewireless device 2050 may be operative to determine a transmission modeamong alternative transmission modes for transmitting the uplinksignaling message, as described above. The wireless device 2050 may alsobe operative to transmit the uplink signaling message according to thedetermined transmission mode, via the communication interface circuit2053.

The functionality split embodiment is illustrated in FIG. 20b . In suchan embodiment, network functions serving the wireless device 2050 overthe first wireless link are split between the first network element 2000and a second network element 2020. Network functions serving thewireless device 2050 over the second wireless link are split between thefirst network element 2000 and a third network element 2030.Furthermore, FIG. 20b illustrates that the first, second and thirdnetwork elements, 2000, 2020, 2030, may be part of one physical networknode 2040. However, any other physical deployment or grouping of thenetwork elements is possible. They may e.g. all be separate physicalnodes, or the second and the third network element may be part of thesame physical network node although separate from the first networkelement.

In an alternative way to describe the embodiment in FIG. 20a shown inFIG. 20c , the wireless device 2050 may comprise a determining module2055 adapted to determine a transmission mode among alternativetransmission modes for transmitting the uplink signaling message. Thealternative transmission modes comprise: transmitting on the firstwireless link; transmitting on the second wireless link; andtransmitting on both the first and the second wireless links. Thewireless device 2050 may also comprise a transmitting module 2056adapted to transmit the uplink signaling message according to thedetermined transmission mode.

In embodiments, the wireless device 2050 may also comprise a receivingmodule adapted to receive information from the first network element2000, indicating at least one of the alternative transmission modes. Thedetermining module 2055 may be adapted to determine the transmissionmode based on the received information. In a further embodiment, thedetermining module 2055 may be adapted to determine the transmissionmode based on criteria for determining transmission mode. As anotheroption, the receiving module may be adapted to receive the criteria fordetermining transmission mode from the first network element 2000.

In other embodiments, the determining module 2055 may be adapted todetermine the transmission mode by obtaining the channel quality of atleast one of the first and the second wireless links, and by determiningthe transmission mode based on the obtained channel quality. Theobtaining may comprise at least one of measuring the channel quality andreceiving the channel quality from the first network element 2000. Inembodiments, the wireless device 2050 may comprise an obtaining moduleadapted to obtain the channel quality of both the first and the secondwireless links, and the determining module 2055 may be adapted todetermine the transmission mode based on the obtained channel quality bydetermining to transmit the uplink signaling message on the wirelesslink with highest obtained channel quality, when the highest obtainedchannel quality is equal to or above a threshold value. When the highestobtained channel quality is below the threshold value, the determiningmodule 2055 may be adapted to determine the transmission mode based onthe obtained channel quality by determining to transmit the uplinksignaling message on both the first and the second wireless links.

In embodiments, the determining module 2055 may be adapted to determinethe transmission mode by determining to transmit the uplink signalingmessage on both the first and the second wireless links, and bydetermining to repeatedly retransmit the uplink signaling message onboth wireless links until an acknowledgement of the uplink signalingmessage is received on at least one of the first and the second wirelesslinks.

As an alternative, the determining module 2055 may be adapted todetermine the transmission mode by determining to transmit the uplinksignaling message on the first wireless link, and by determining toretransmit the uplink signaling message on the second wireless link ifno acknowledgement is received for the uplink signaling messagetransmitted on the first wireless link.

In any of the embodiments above, the uplink signaling message may be ameasurement report. Furthermore, the first and the second wireless linksmay be both associated with one RAT, or each associated with respectivedifferent RATs.

The modules described above are functional units which may beimplemented in hardware, software, firmware or any combination thereof.In one embodiment, the modules are implemented as a computer programrunning on a processor.

In still another alternative way to describe the embodiment in FIG. 20a, the wireless device 2050 may comprise a Central Processing Unit (CPU)which may be a single unit or a plurality of units. Furthermore, thewireless device 2050 may comprise at least one computer program product(CPP) with a computer readable medium in the form of a non-volatilememory, e.g. an EEPROM (Electrically Erasable Programmable Read-OnlyMemory), a flash memory or a disk drive. The CPP may comprise a computerprogram stored on the computer readable medium, which comprises codemeans which when run on the CPU of the wireless device 2050 causes thewireless device 2050 to perform the methods described earlier inconjunction with FIGS. 18a through 18e . In other words, when said codemeans are run on the CPU, they correspond to the processing circuit 2051of the wireless device 2050 in FIG. 20 a.

Network Element

An embodiment of a first network element 2000 is schematicallyillustrated in the block diagram in FIG. 20a . The first network element2000 is configured to enable the wireless device 2050 to transmit anuplink signaling message in a wireless communication network. The firstnetwork element 2000 may in embodiments be comprised in an eNodeB of anLTE network. The wireless device 2050 is connectable to the firstnetwork element 2000 over at least a first and a second wireless link.The first network element 2000 is further configured to determine atleast one transmission mode among alternative transmission modes fortransmitting the uplink signaling message. The alternative transmissionmodes comprise: transmitting on the first wireless link; transmitting onthe second wireless link; and transmitting on both the first and thesecond wireless links. The determining is based on criteria fordetermining transmission mode. The first network element 2000 is alsoconfigured to transmit information to the wireless device 2050 enablingthe wireless device 2050 to determine transmission mode for transmittingthe uplink signaling message. The information comprise an indication ofthe determined at least one transmission mode.

The first network element 2000 may in embodiments be configured totransmit information to the wireless device 2050 further comprisingcriteria for determining transmission mode.

Furthermore, the first network element 2000 may in embodiments beconfigured to receive the uplink signaling message from the wirelessdevice 2050 in accordance with one of the alternative transmissionmodes.

In any of the embodiments above, the uplink signaling message may be ameasurement report. Furthermore, the first and the second wireless linksmay be both associated with one RAT, or each associated with respectivedifferent RATs.

The functionality split described e.g. with reference to FIG. 13 abovemay also be applied in embodiments. In such an embodiment, networkfunctions serving the wireless device over the first wireless link aresplit between the first network element and a second network element.Network functions serving the wireless device over the second wirelesslink are split between the first network element and a third networkelement. In the example scenario in FIGS. 15 and 16 the first networkelement correspond to the eNB-a, the second network element correspondsto eNB-s1, and the third network element corresponds to eNB-s2. Asdescribed above, the network functions of the first network element maybe asynchronous network functions, and the network functions of thesecond and third network elements may be synchronous network functions.The synchronous network functions of the second network element may haverequirements on processing timing which are strictly dependent on timingof the first wireless link. The synchronous network functions of thethird network element may have requirements on processing timing whichare strictly dependent on timing of the second wireless link.Furthermore, the asynchronous network functions may have requirements onprocessing timing not strictly dependent on the timing of any of thefirst or second wireless links.

As illustrated in FIG. 20a , the first network element 2000 may comprisea processing circuit 2001 and a memory 2002 in embodiments of theinvention. The first network element 2000 may also comprise acommunication interface circuit 2003 configured to communicate with thewireless device 2050 over the first and second wireless links. Thecommunication interface circuit 2003 may in embodiments comprise atransceiver adapted to communicate wirelessly with the wireless device2050. The memory 2002 may contain instructions executable by saidprocessing circuit 2001, whereby the first network element 2000 may beoperative to determine at least one transmission mode among alternativetransmission modes for transmitting the uplink signaling message. Thealternative transmission modes comprise: transmitting on the firstwireless link; transmitting on the second wireless link; andtransmitting on both the first and the second wireless links. Thedetermining is based on criteria for determining transmission mode.

The first network element 2000 may also be operative to transmitinformation to the wireless device 2050 enabling the wireless device2050 to determine transmission mode for transmitting the uplinksignaling message. The information comprises an indication of thedetermined at least one transmission mode.

In an alternative way to describe the first network element, illustratedin FIG. 20c , the first network element 2000 may comprise a determiningmodule 2005 adapted to determine at least one transmission mode amongalternative transmission modes for transmitting the uplink signalingmessage. The alternative transmission modes comprise: transmitting onthe first wireless link; transmitting on the second wireless link; andtransmitting on both the first and the second wireless links. Thedetermining is based on criteria for determining transmission mode. Thefirst network element 2000 may also comprise a transmitting module 2006adapted to transmit information to the wireless device 2050 enabling thewireless device 2050 to determine transmission mode for transmitting theuplink signaling message. The information comprise an indication of thedetermined at least one transmission mode.

In embodiments, the transmitting module 2006 may be adapted to transmitinformation to the wireless device 2050 further comprising criteria fordetermining transmission mode. In any of the embodiments, the uplinksignaling message may be a measurement report. Furthermore, the firstand the second wireless links may be both associated with one RAT, oreach associated with respective different RATs.

The modules described above are functional units which may beimplemented in hardware, software, firmware or any combination thereof.In one embodiment, the modules are implemented as a computer programrunning on a processor.

In still another alternative way to describe the embodiment in FIG. 20a, the first network element 2000 may comprise a Central Processing Unit(CPU) which may be a single unit or a plurality of units. Furthermore,the first network element 2000 may comprise at least one computerprogram product (CPP) with a computer readable medium in the form of anon-volatile memory, e.g. an EEPROM (Electrically Erasable ProgrammableRead-Only Memory), a flash memory or a disk drive. The CPP may comprisea computer program stored on the computer readable medium, whichcomprises code means which when run on the CPU of the first networkelement 2000 causes the first network element 2000 to perform the methoddescribed earlier in conjunction with FIG. 19. In other words, when saidcode means are run on the CPU, they correspond to the processing circuit2001 of the first network element 2000 in FIG. 20 a.

The above mentioned and described embodiments are only given asnon-limiting examples. Other solutions, uses, objectives, and functionswithin the scope of the accompanying patent claims may be possible.

1. A method for transmitting an uplink measurement report message in awireless dual connectivity communication network, the method beingperformed in a wireless device connected to the network over at least afirst and a second wireless link, the method comprising: receivinginformation for transmitting the uplink measurement report message fromthe network, indicating at least one of alternative transmission modes,the alternative transmission modes comprising: transmitting on the firstwireless link; transmitting on the second wireless link; andtransmitting on both the first and the second wireless links;determining the transmission mode based on the received information andbased on a type of measurement report; and transmitting the uplinkmeasurement report message according to the determined transmissionmode.
 2. The method according to claim 1, wherein the information fromthe network, indicating at least one of the alternative transmissionmodes is received via a radio resource control, RRC, message.
 3. Themethod according to claim 1, wherein the determining is further based oncriteria for determining transmission mode.
 4. The method according toclaim 3, further comprising: receiving the criteria for determiningtransmission mode from the network.
 5. The method according to claim 3,wherein the criteria for determining transmission mode is related to atleast one of: a channel quality of at least one of the first and thesecond wireless links; a load on at least one of the first and thesecond wireless links; a wireless device capability of using at leastone of the first and the second wireless links; a quality of service ofa bearer associated with the uplink measurement report message; alatency of at least one of the first and the second wireless links; atransmission mode of a downlink signaling message to which the uplinkmeasurement report message is a response; whether the uplink measurementreport message is acknowledged or not; use of carrier aggregation on atleast one of the first and the second wireless links; a speed of thewireless device; a quality of service associated with at least one ofthe first and the second wireless links; a pre-determined rule fordetermining the transmission mode; a random selection of at least one ofthe first and the second wireless links.
 6. A wireless device configuredto transmit an uplink measurement report message in a wireless dualconnectivity communication network, the wireless device beingconnectable to the network over at least a first and a second wirelesslink, the wireless device being further configured to: receiveinformation for transmitting the uplink measurement report message fromthe network, indicating at least one of alternative transmission modes,the alternative transmission modes comprising: transmitting on the firstwireless link; transmitting on the second wireless link; andtransmitting on both the first and the second wireless links; determinethe transmission mode based on the received information and based on atype of measurement report; and transmit the uplink measurement reportmessage according to the determined transmission mode.
 7. The wirelessdevice according to claim 6, wherein the information from the network,indicating at least one of the alternative transmission modes isreceived via a radio resource control, RRC, message.
 8. The wirelessdevice according to claim 6, further configured to determine thetransmission mode based on criteria for determining transmission mode.9. The wireless device according to claim 8, further configured toreceive the criteria for determining transmission mode from the network.10. The wireless device according to claim 8, further configured todetermine the transmission mode by being configured to: obtain thechannel quality of at least one of the first and the second wirelesslinks, wherein the obtaining comprises at least one of measuring thechannel quality and receiving the channel quality from the network, anddetermine the transmission mode based on the obtained channel quality.11. A non-transitory computer readable medium comprising instructionsexecutable by processing circuitry of a wireless device connected to awireless dual connectivity communication network over at least a firstand a second wireless link, whereby the wireless device is operable to:receive information for transmitting the uplink measurement reportmessage from the network, indicating at least one of alternativetransmission modes, the alternative transmission modes comprising:transmitting on the first wireless link; transmitting on the secondwireless link; and transmitting on both the first and the secondwireless links; determine the transmission mode based on the receivedinformation and based on a type of measurement report; and transmit theuplink measurement report message according to the determinedtransmission mode.